From: Paolo Bonzini <pbonzini@redhat.com>
To: Peter Maydell <peter.maydell@linaro.org>,
QEMU Developers <qemu-devel@nongnu.org>
Subject: Re: QEMU device refcounting when device creates a container MR
Date: Wed, 9 Mar 2022 17:21:47 +0100 [thread overview]
Message-ID: <4eb4bb05-814b-c28c-c2f4-0f5f5582301b@redhat.com> (raw)
In-Reply-To: <CAFEAcA87VaeHzW4qbHn+UKjh9gMQbKNcN5ytXBS1MUPSapdhYw@mail.gmail.com>
On 3/9/22 11:33, Peter Maydell wrote:
> Hi; does anybody know how device reference counting is supposed
> to work when the device creates a "container" MemoryRegion which
> it then puts some of its own subregions in to?
>
> As far as I can see when you do memory_region_add_subregion it
> increases the refcount on the owner of the subregion. So if a
> device creates a container MR in its own init or realize method
> and adds sub-MRs that it owns to that container, this increases
> the refcount on the device permanently, and so the device won't
> ever be deinited.
The unparent method is supposed to break reference cycles.
In the case of QOM, unparent calls unrealize, so unrealize should remove
the subregions it created.
Paolo
next prev parent reply other threads:[~2022-03-09 16:24 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-09 10:33 QEMU device refcounting when device creates a container MR Peter Maydell
2022-03-09 10:40 ` Philippe Mathieu-Daudé
2022-03-10 13:19 ` Peter Xu
2022-03-10 13:45 ` Peter Maydell
2022-03-11 2:19 ` Peter Xu
2022-03-09 16:21 ` Paolo Bonzini [this message]
2022-03-09 16:53 ` Peter Maydell
2022-03-09 16:56 ` Peter Maydell
2022-03-10 15:36 ` Igor Mammedov
2022-03-10 16:05 ` Peter Maydell
2022-03-10 16:30 ` Igor Mammedov
2022-03-10 17:11 ` Peter Maydell
2022-03-18 17:13 ` Igor Mammedov
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